/*
 * ElementMapLabel.java July 2007
 *
 * Copyright (C) 2007, Niall Gallagher <niallg@users.sf.net>
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
 * implied. See the License for the specific language governing
 * permissions and limitations under the License.
 */

package wx.xml.simpleframework.xml.core;

import java.lang.annotation.Annotation;

import wx.xml.simpleframework.xml.ElementMap;
import wx.xml.simpleframework.xml.strategy.Type;
import wx.xml.simpleframework.xml.stream.Format;
import wx.xml.simpleframework.xml.stream.Style;

/**
 * The <code>ElementMapLabel</code> represents a label that is used
 * to represent an XML element map in a class schema. This element
 * list label can be used to convert an XML node into a map object
 * of composite or primitive key value pairs. Each element converted
 * with the converter this creates must be an XML serializable element.
 *
 * @author Niall Gallagher
 * @see wx.xml.simpleframework.xml.ElementMap
 */
class ElementMapLabel extends TemplateLabel {

    /**
     * This is the decorator that is associated with the element.
     */
    private Decorator decorator;

    /**
     * This contains the details of the annotated contact object.
     */
    private Introspector detail;

    /**
     * This references the annotation that the field uses.
     */
    private ElementMap label;

    /**
     * This is a cache of the expression for this element map.
     */
    private Expression cache;

    /**
     * This is the format used to style the elements for this.
     */
    private Format format;

    /**
     * The entry object contains the details on how to write the map.
     */
    private Entry entry;

    /**
     * This is the name of the element for this label instance.
     */
    private String override;

    /**
     * This is the name of the XML entry from the annotation.
     */
    private String parent;

    /**
     * This is the path of the element for this label instance.
     */
    private String path;

    /**
     * This is the name of the element for this label instance.
     */
    private String name;

    /**
     * Represents the type of objects this map object will hold.
     */
    private Class[] items;

    /**
     * This is the type of map object this list will instantiate.
     */
    private Class type;

    /**
     * This is used to determine if the attribute is required.
     */
    private boolean required;

    /**
     * This is used to determine if the attribute is inline.
     */
    private boolean inline;

    /**
     * This is used to determine if the attribute is data.
     */
    private boolean data;

    /**
     * Constructor for the <code>ElementMapLabel</code> object. This
     * creates a label object, which can be used to convert an XML
     * node to a <code>Map</code> of XML serializable objects.
     *
     * @param contact this is the contact that this label represents
     * @param label   the annotation that contains the schema details
     * @param format  this is the format used to style this label
     */
    public ElementMapLabel(Contact contact, ElementMap label, Format format) {
        this.detail = new Introspector(contact, this, format);
        this.decorator = new Qualifier(contact);
        this.entry = new Entry(contact, label);
        this.required = label.required();
        this.type = contact.getType();
        this.inline = label.inline();
        this.override = label.name();
        this.data = label.data();
        this.format = format;
        this.label = label;
    }

    /**
     * This is used to acquire the <code>Decorator</code> for this.
     * A decorator is an object that adds various details to the
     * node without changing the overall structure of the node. For
     * example comments and namespaces can be added to the node with
     * a decorator as they do not affect the deserialization.
     *
     * @return this returns the decorator associated with this
     */
    public Decorator getDecorator() throws Exception {
        return decorator;
    }

    /**
     * This method returns a <code>Converter</code> which can be used to
     * convert an XML node into an object value and vice versa. The
     * converter requires only the context object in order to perform
     * serialization or deserialization of the provided XML node.
     *
     * @param context this is the context object for the serialization
     * @return this returns an object that is used for conversion
     */
    @Override
    public Converter getConverter(Context context) throws Exception {
        Type type = getMap();

        if (!label.inline()) {
            return new CompositeMap(context, entry, type);
        }
        return new CompositeInlineMap(context, entry, type);
    }

    /**
     * This is used to provide a configured empty value used when the
     * annotated value is null. This ensures that XML can be created
     * with required details regardless of whether values are null or
     * not. It also provides a means for sensible default values.
     *
     * @param context this is the context object for the serialization
     * @return this returns the string to use for default values
     */
    @Override
    public Object getEmpty(Context context) throws Exception {
        Type    map     = new ClassType(type);
        Factory factory = new MapFactory(context, map);

        if (!label.empty()) {
            return factory.getInstance();
        }
        return null;
    }

    /**
     * This is used to acquire the dependent type for the annotated
     * list. This will simply return the type that the map object is
     * composed to hold. This must be a serializable type, that is,
     * a type that is annotated with the <code>Root</code> class.
     *
     * @return this returns the component type for the map object
     */
    @Override
    public Type getDependent() throws Exception {
        Contact contact = getContact();

        if (items == null) {
            items = contact.getDependents();
        }
        if (items == null) {
            throw new ElementException(this, "Unable to determine type for %s", contact);
        }
        if (items.length == 0) {
            return new ClassType(Object.class);
        }
        return new ClassType(items[0]);
    }

    /**
     * This is used to either provide the entry value provided within
     * the annotation or compute a entry value. If the entry string
     * is not provided the the entry value is calculated as the type
     * of primitive the object is as a simplified class name.
     *
     * @return this returns the name of the XML entry element used
     */
    @Override
    public String getEntry() throws Exception {
        Style style = format.getStyle();

        if (detail.isEmpty(parent)) {
            parent = detail.getEntry();
        }
        return style.getElement(parent);
    }

    /**
     * This is used to acquire the name of the element or attribute
     * that is used by the class schema. The name is determined by
     * checking for an override within the annotation. If it contains
     * a name then that is used, if however the annotation does not
     * specify a name the the field or method name is used instead.
     *
     * @return returns the name that is used for the XML property
     */
    public String getName() throws Exception {
        if (name == null) {
            Style  style = format.getStyle();
            String value = entry.getEntry();

            if (!label.inline()) {
                value = detail.getName();
            }
            name = style.getElement(value);
        }
        return name;
    }

    /**
     * This is used to acquire the path of the element or attribute
     * that is used by the class schema. The path is determined by
     * acquiring the XPath expression and appending the name of the
     * label to form a fully qualified path.
     *
     * @return returns the path that is used for the XML property
     */
    @Override
    public String getPath() throws Exception {
        if (path == null) {
            Expression expression = getExpression();
            String     name       = getName();

            path = expression.getElement(name);
        }
        return path;
    }

    /**
     * This method is used to return an XPath expression that is
     * used to represent the position of this label. If there is no
     * XPath expression associated with this then an empty path is
     * returned. This will never return a null expression.
     *
     * @return the XPath expression identifying the location
     */
    @Override
    public Expression getExpression() throws Exception {
        if (cache == null) {
            cache = detail.getExpression();
        }
        return cache;
    }

    /**
     * This returns the map type for this label. The primary type
     * is the type of the <code>Map</code> that this creates. The key
     * and value types are the types used to populate the primary.
     *
     * @return this returns the map type to use for the label
     */
    private Type getMap() {
        return new ClassType(type);
    }

    /**
     * This acquires the annotation associated with this label. This
     * is typically the annotation acquired from the field or method.
     * However, in the case of unions this will return the actual
     * annotation within the union group that this represents.
     *
     * @return this returns the annotation that this represents
     */
    @Override
    public Annotation getAnnotation() {
        return label;
    }

    /**
     * This acts as a convenience method used to determine the type of
     * contact this represents. This is used when an object is written
     * to XML. It determines whether a <code>class</code> attribute
     * is required within the serialized XML element, that is, if the
     * class returned by this is different from the actual value of the
     * object to be serialized then that type needs to be remembered.
     *
     * @return this returns the type of the contact class
     */
    @Override
    public Class getType() {
        return type;
    }

    /**
     * This is used to acquire the contact object for this label. The
     * contact retrieved can be used to set any object or primitive that
     * has been deserialized, and can also be used to acquire values to
     * be serialized in the case of object persistence. All contacts
     * that are retrieved from this method will be accessible.
     *
     * @return returns the contact that this label is representing
     */
    @Override
    public Contact getContact() {
        return detail.getContact();
    }

    /**
     * This is used to acquire the name of the element or attribute
     * as taken from the annotation. If the element or attribute
     * explicitly specifies a name then that name is used for the
     * XML element or attribute used. If however no overriding name
     * is provided then the method or field is used for the name.
     *
     * @return returns the name of the annotation for the contact
     */
    @Override
    public String getOverride() {
        return override;
    }

    /**
     * This is used to determine whether the annotation requires it
     * and its children to be written as a CDATA block. This is done
     * when a primitive or other such element requires a text value
     * and that value needs to be encapsulated within a CDATA block.
     *
     * @return currently the element list does not require CDATA
     */
    @Override
    public boolean isData() {
        return data;
    }

    /**
     * This is used to determine if the label is a collection. If the
     * label represents a collection then any original assignment to
     * the field or method can be written to without the need to
     * create a new collection. This allows obscure collections to be
     * used and also allows initial entries to be maintained.
     *
     * @return true if the label represents a collection value
     */
    @Override
    public boolean isCollection() {
        return true;
    }

    /**
     * This is used to determine whether the XML element is required.
     * This ensures that if an XML element is missing from a document
     * that deserialization can continue. Also, in the process of
     * serialization, if a value is null it does not need to be
     * written to the resulting XML document.
     *
     * @return true if the label represents a some required data
     */
    public boolean isRequired() {
        return required;
    }

    /**
     * This is used to determine whether the list has been specified
     * as inline. If the list is inline then no overrides are needed
     * and the outer XML element for the list is not used.
     *
     * @return this returns whether the annotation is inline
     */
    @Override
    public boolean isInline() {
        return inline;
    }

    /**
     * This is used to describe the annotation and method or field
     * that this label represents. This is used to provide error
     * messages that can be used to debug issues that occur when
     * processing a method. This will provide enough information
     * such that the problem can be isolated correctly.
     *
     * @return this returns a string representation of the label
     */
    public String toString() {
        return detail.toString();
    }
}
